Installing a Victron 702 w/ OEM Aux battery

Redskeets

Member
Ok, that brings me back to my initial question. You mentioned (I think it was you) your BMV also accounts for amperage provided by your alternator when the engine is running. I assumed that this was because the shunt is tied to the starter battery. Looks like another misassumption. Do you know what route your BMV is picking up your alternator amperage? Once again, I thought this was through the starter battery. Def green at this stuff, but getting better, painfully.
 

sprinterPaul

Well-known member
Ok, that brings me back to my initial question. You mentioned (I think it was you) your BMV also accounts for amperage provided by your alternator when the engine is running. I assumed that this was because the shunt is tied to the starter battery. Looks like another misassumption. Do you know what route your BMV is picking up your alternator amperage? Once again, I thought this was through the starter battery. Def green at this stuff, but getting better, painfully.


I have a battery combiner/isolator. Surepower 1315-200. You have a relay. Same concept. Ok.

When the relay is engaged and the batteries combine. The alt will sense a draw(?) i guess and feed the amps in to charge. Need an ee for the right terms. But anyway, you will see amps coming in when combined.

I see the amps when i monitor my bmv. I use the victron app. Highly recommended. Use Bluetooth dongle.
 

sprinterPaul

Well-known member
You might want to read the auxiliary battery retrofit guide from MB. Shows how your aux battery is hooked up. A quick google will find it for you.
 

Redskeets

Member
U that man! Thanks Paul! Believe it or not I have the BT dongle as well. Works wonderfully, just couldn’t figure out why my BMV wasn’t picking up the alternator AMPs when engine is running. Hopefully when I connect the shunt to negative on house battery all will be good. Thx again!:bow:
 

sprinterPaul

Well-known member
U that man! Thanks Paul! Believe it or not I have the BT dongle as well. Works wonderfully, just couldn’t figure out why my BMV wasn’t picking up the alternator AMPs when engine is running. Hopefully when I connect the shunt to negative on house battery all will be good. Thx again!:bow:
Welcome. Just hook it up and test. You will probably be surprised and off onto the next task.
 

sprinterPaul

Well-known member
Paul, what sort of amperage are you receiving back into your bank while driving, on average?


It depends on how discharged your battery is. Could be 8-10 amps. Could be 80. Usually it's just pushing in around 30A into my 250ah bank when I'm about 85% SOC. You have a 95ah battery.
 
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Redskeets

Member
Hey Paul I was just thinking about what you mentioned regarding having one shunt per battery back. Looking over the diagram I sent it shows both the starter and the house battery negative leads going to the shunt? Any idea what’s up with that?
 

sprinterPaul

Well-known member
Hey Paul I was just thinking about what you mentioned regarding having one shunt per battery back. Looking over the diagram I sent it shows both the starter and the house battery negative leads going to the shunt? Any idea what’s up with that?


Look closer. It is the same thing as chassis ground. Which it is already connected to.
 

Wildebus

Member
That Victron diagram is a little unfortunate as it kind of implies you have the starter battery going to a connection on the shunt, albeit the load side which is 100% the same as ground/chassis. Essentially ignore the dotted lines.

Redskeets, I think you are trying to do something which you cannot with a single device. What SprinterPaul has told you in his various replies is spot on.

To recap:
The Victron Shunt attaches to the leisure battery exactly as the diagram shows. You do not do ANYTHING regarding Starter battery connections and cabling.
With the shunt installed, the 702 will record and display the total current going into OR out of the Leisure battery.
If the alternator is providing a charge to your Leisure Battery, the 702 will show THAT charge, not the total alternator output.
If at the same time you have a load on the Leisure Battery that comes into play. For example, if you have an inverter running that is pulling 350W - that will be drawing around 25A or so from your battery. If the Alternator is stuffing in 40A into that battery at the same time, the BMV-702 will show 15A charge into the battery, and NOT 40A.

You seem particularly keen on monitoring the alternator output? If this is the case then you need to get a dedicated monitor for that. This would not be that hard to do, but you can't do it with the BMV-702 when connected to the Leisure (House) Batteries in the normal manner.
If it just a matter of curiosity, then a clamp meter might tell you what you want to know?
 

Redskeets

Member
Wildebus, thank you for additional explanation! Why I am so keen on getting alternator amperage is because that is really the only portion of my 702 that has not been working. And with both of your help it looks like I know why now. My current shunt connection is grounded to chassis. Works to read all loads very accurately, but never registered the and additional amperage with engine running. I’m going to relocate my shunt and wire as you both have advised on Monday, directly to the negative. That should do the trick.
 
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Redskeets

Member
I have relocated shunt in engine compartment (right next to OEM aux/house battery). I have run the negative from OEM aux battery directly to the line side of shunt. And I have connected the load side of shunt directly to the chassis (where the original OEM aux battery comes connected). For the BMV to be able to monitor all of my loads I assume I also need to run a wire all the way back inside to my loads, correct? If not, I don't see how the monitor will be able to pick up any negative readings?
 

dowdelst

Member
Hey guys,

I skimmed this quickly, so apologies for missing it, but I was wondering if any of you use the second channel of the Victrom 702 to monitor the temperature of your house batteries, rather than monitoring the voltage of the starting battery. I saw it in the manual for my 700, which seems to be the same for the 702, except that the 700 only has one channel, hence no capability to monitor my house battery temps. (Feeling buyer's remorse about this here.) Of course, there's a temp sensor that you need to buy for this to work.

It seems more useful for the Victron to provide house battery information that incorporates the battery temperature than to be able to monitor the starting battery voltage (especially if you have some sort of isolation in place). Thoughts?
 

rmplstlskn

Member
Any issues with the shunts getting wet inside the engine compartment?
Thanks everyone for contributing to a very educational thread.
 

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